As officials continued to investigate the deaths of Jennifer Hudson's mother and brother at the family's South Side home in Chicago on Thursday, a detective said police believe the Oscar-winning singer's 7-year-old nephew, Julian King, was probably shot in the SUV where his body was found Monday.

The Associated Press, quoting an anonymous police source, reported that investigators believe King was alive when he left the house where his grandmother and uncle were killed last week. A day after detectives found what they believe was the gun used in the killings, they still would not comment on when they think the boy died.

The Hudson family is planning a private memorial service on Monday for Darnell Donerson, 57, Jason Hudson, 29, and King.

The family has also formed a new foundation for the families of murder victims. In a statement released on Thursday announcing the Hudson-King Foundation for Families of Slain Victims, the family said, "The specific purpose of the Foundation is to care for the needs of families who have lost relatives to a violent crime. This encompasses their basic needs of food, clothing and shelter, as well as grief counseling."

Donations can be sent to:

Hudson-King Foundation
c/o Abrams Garfinkel Margolis Bergson, LLP
Attn: William L. Abrams, Esq.
237 West 35th Street, 4th Floor
New York, NY 10001

People.com reported that the foundation announcement followed a prayer vigil Wednesday night in Chicago. "Jennifer sang her first song in this church — she said her first prayer in this church," her cousin, Shari Nichols Witt, said of the Pleasant Gift Missionary Baptist Church where the vigil was held. The Reverend Jesse Jackson spoke at the vigil and told the magazine that Hudson, 27, and her family "are overwhelmed by the suddenness and the unexpectedness of it all. This family knows triumph, and they also know tragedy."

Police have not yet charged anyone in the slaying, but the estranged husband of Hudson's sister Julia, William Balfour, is being held on an alleged parole violation as a "person of interest" in the case. An unnamed source said to be a friend of the Hudson family told Us Weekly that he tried to warn them about Balfour, also known as "Flex," who reportedly got into a "huge fight" with Julia and Jason Hudson, their mother and the singer's ex-fiancé, James Peyton, about a month ago. "Flex tried to start a fistfight with Jason, and James beat up Flex," the neighbor said, adding that shortly after, Balfour allegedly began to threaten the family, saying he would "kill Julia and mess up everyone in the house."

Balfour's mother has insisted that her son had nothing to do with the murders, though police have said that his alibi has clashed with the account given by his girlfriend, in whose house he was found by police on the day of the murders.

On Thursday, Chicago Police Superintendent Jody Weis said that a .45-caliber handgun was found on Wednesday in a vacant lot a block away from where the SUV was parked; preliminary tests have suggested that the gun used in the murders was a .45.